How do DNA Test Results Relate to Genealogical Research?

I received a question concerning a DNA test that shows African-American heritage. As a rule, I have somewhat avoided the issue of DNA testing for the main reason that my experience has shown that many of the people who participate either do not understand the results, are unpleasantly surprised by the results or have unreasonable expectations as to what the DNA test will show. I did not wish to appear to be "promoting" DNA testing. Notwithstanding this statement, click here for a link to a list of DNA testing companies offering direct-to-consumer (DTC) DNA tests for genealogy, deep ancestry and ethnicity.

I last wrote about this subject in January.
Can DNA Testing Help You Find Your Ancestors? -- Part One
Can DNA Testing Help You Find Your Ancestors? Part Two

I decided it was time to update my thoughts on this rapidly changing area of genealogical research.
As a long time trial attorney, I am well aware of the important part DNA evidence has played in the legal community. But I am also aware of the limitations of the testing procedures. DNA tests have become a staple in paternity suits and many criminal cases. Most of the information provided about DNA testing has traditionally been couched in very technical "scientific" jargon. The jargon is not particularly helpful in explaining how DNA testing will help you with your genealogical research. DNA testing is not infallible. The test has to be performed correctly in the first instance and then the results have to be interpreted correctly. During the entire testing procedure, there have to be assurances that the DNA sample presented for testing is not contaminated.

Most of the discussion I see about DNA testing in the genealogical community revolves around the concept that the testing puts genealogy on a scientific basis. It is scientific but the results are based on probability, not certainty. It is true that the probability, in some types of cases, can be almost certain, but there is still a degree of error. This does not differ from the consideration of historical documentary evidence. All historical (and genealogical) conclusions are subject to revision based on additional evidence, i.e. documentation.

I neither discourage or encourage genealogists to obtain DNA testing for the reasons I mentioned previously. In any event, I would encourage genealogists who seek resolution of genealogical relationships through DNA testing to take the time to explore exactly what the proposed DNA test will and will not show about any particular ancestry. If a DNA test motivates you to begin researching your genealogy, then it is a good thing.

The basic issue with DNA testing and genealogy is testing that is done without the supporting document based genealogical research. In almost every case, it is important that the "paper" research be done in order to establish a reasonable basis for conducting a DNA test. DNA testing is in its area of expertise when it is used to determine if two people are related. Obviously, the more distant the relationship, the less accurate the DNA test will be. It also helps to have a large base of DNA contributors to use for drawing conclusions. This is where the DNA world is changing rapidly.

One of the major difficulties faced by genealogists in the past has been obtaining the cooperation of potential relatives to determine the relationship or lack of a relationship with a researched ancestor. That issue is changing rapidly. Two of the larges online genealogical database companies, Ancestry.com and MyHeritage.com, have taken significant steps to increase the availability of DNA testing and both provide DNA testing. In the case of MyHeritage.com, that company has also indicated that they may be adding the ability to share DNA information through their online family trees. In doing this, MyHeritage.com is making a significant advance. Traditional genealogists will now be able to judge, first hand, whether or not the DNA evidence becomes useful.